There are numerous products formed using heat sealable materials, including pouches and other containers. They are manufactured by heat sealing together different layers of the materials in multiple locations to achieve the various sizes and shapes desired. U.S. Pat. Nos. 5,536,542 and 5,484,375 generally disclose articles created by heat sealing polymeric layers together.
It is often desirable to heat seal a multi-layer product in an area at a given temperature while not affecting one or more of the layers for design or functional reasons. Currently, this is achieved by introducing barrier layers such as paper, treating the layer that is to be protected with a lubricant or paint, or using a mechanical process to prevent a heat seal from occurring between certain layers in that area. This inevitably leads to additional multi-step processes which add time and cost to the manufacturing process. It would be advantageous to effect heat seals between layers in some areas at one temperature and in other areas at a different temperature without the need for additional intermediary steps.
U.S. Pat. No. 6,996,951 discloses a flexible multi-compartment container with peelable seals and a method for making such a container. In one specific embodiment, the container includes multiple layers, with an outer layer having a higher melting temperature than an inner seal layer. U.S. Pat. No. 4,147,827 discloses a method for the production of heat sealable co-extruded films having a high melting point core layer coated on at least one side with a lower melting point skin layer.
Thus, while the above references describe articles created by sealing together multiple layers of material, some of which may have different melting temperatures, none of them discloses, teaches or suggests a product formed of multiple layers that are heat sealed together wherein, in some areas, the materials forming the product are heat sealable at a lower temperature, and in other areas, the materials forming the product are heat sealable at a higher temperature, thereby allowing for heat sealing of discrete areas of the product in discrete steps.